This invention relates to automatic transmissions, such as motor vehicle transmissions, having three planetary gear sets.
While conventional automatic transmissions generally have three or four gear stages, the provision of additional gear stages can improve riding comfort and reduce fuel consumption. It can be assumed that, as the number of planetary gear stages is increased, the space requirement as well as the number of planetary gear sets or planetary gear elements and the number of shifting components, such as clutches and brakes, will increase sharply. In the development of modern multispeed automatic transmissions, one objective has therefore been to further increase the number of gear stages while, at the same time, keeping the space requirement and the number of shifting components as small as possible.
An automatic transmission that attempts to meet these requirements is described in the Korean periodical SAE, Vol. 1, 1991, page 285. The automatic transmission represented in FIG. 10 of that publication is designed as a six-stage transmission in which three planetary gear sets are arranged one after another in series and connected to each other to provide six forward speeds and one reverse speed using five shifting components, i.e., brakes or clutches.